Art Morrison Enterprises

Multilink IRS Setup & Assembly Manual

8/13/2018 Rev 6

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Contents Introduction .................................................................................................................................... 3

Toe Link Eccentric ........................................................................................................................ 3

Powdercoating ............................................................................................................................ 3

IRS Assembly Steps ......................................................................................................................... 4

1. Backing plates/Knuckles/Hubs ............................................................................................. 4

2. Differential ........................................................................................................................... 4

3. Axles ..................................................................................................................................... 4

4. Anti-Sway Bar ....................................................................................................................... 4

5. Control Arms ........................................................................................................................ 5

6. Toe Link ................................................................................................................................ 5

7. Knuckle Assembly ................................................................................................................ 5

8. Final Torque of UCA Bolts and Axle Nut .............................................................................. 5

9. Cradle Bushings .................................................................................................................... 6

Finalizing the Installation ................................................................................................................ 6

1. Cradle Installation ................................................................................................................ 6

2) Coilover Installation ............................................................................................................. 7

3) Wheel Alignment ................................................................................................................. 7

Technical Notes ............................................................................................................................... 7

Choosing Spring Rates ................................................................................................................. 7

Adjusting Alignment Settings ...................................................................................................... 8

Toe Link Eccentric Adjustment .................................................................................................... 8

Bumpstops ................................................................................................................................... 9

Wheel Sizes ................................................................................................................................. 9

Parking Brake ............................................................................................................................. 10

Figure 1 - Knuckle Assembly ....................................................................................................................... 11

Figure 2 - Knuckle Assembly ....................................................................................................................... 12

Figure 3 - Differential Assembly .................................................................................................................. 13

Figure 4 - Differential Assembly .................................................................................................................. 14

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Figure 5 - Sway Bar Assembly ..................................................................................................................... 15

Figure 6 - Upper Control Arm Assembly ..................................................................................................... 16

Figure 7 - Front Lower Control Arm Assembly ............................................................................................ 17

Figure 8 - Rear Lower Control Arm Assembly ............................................................................................. 18

Figure 9 – Toe Link Assembly ...................................................................................................................... 19

Figure 10 - Ride Height Specification .......................................................................................................... 20

Figure 11 - LH Link Length Worksheet ........................................................................................................ 21

Figure 12 - RH Link Length Worksheet ........................................................................................................ 22

Figure 13 - Fasteners & Torque Specifications ........................................................................................... 23

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Introduction Important! Please Read Before Disassembly

Toe Link Eccentric

Art Morrison Enterprises has taken many steps to ensure the performance of your new

suspension system is as high as it can possibly be. One important aspect to obtaining this

performance level is the adjustment of the toe-link eccentric, which is preset at Art Morrison

Enterprises.

The adjustment of the toe link does not adjust toe in/out, but actually the toe curve or

“bumpsteer”. The bumpsteer curve has been engineered to steer the rear of the vehicle into a

corner in a safe manner and the adjustment of the eccentric will control the amount of steer

experienced while cornering. Track vehicles will greatly benefit from this method of

adjustment as it allows high horsepower vehicles to control the effects of throttle steer, and

street vehicles will have enhanced turn-in response that further enhances vehicle control. Art

Morrison Enterprises will have a pre-set adjustment that will work for most vehicles that will

enhance handling without adding oversteer. Before disassembling your IRS for finishing, please

mark the location (LH or RH) of each eccentric, and the indicator line that lines up with the

indicator slot in the cradle bracket. Do not skip this step!

To ease alignment, the IRS has been pre-aligned at Art Morrison Enterprises to basic settings to

allow you to drive the vehicle to an alignment shop. These settings are not intended for long-

term use. To maintain this alignment after disassembly for finishing, write down the bolt-to-

bolt centerline measurements for each adjustable link (both lower control arms and toe link) on

the provided worksheets (Figure 11 & 12). Be sure to mark each control arm/link with a LH or

RH designation to avoid confusion.

Powdercoating

If you plan on powdercoating your IRS, please note the thickness of the powdercoat will

typically make the bolt holes too small for a bolt to pass through. Before assembly, run a file

through each hole until a bolt can fit. Depending on the coating thickness, the eccentric stops

may need to be filed until the eccentric washer sits flush on the bracket.

When powdercoating control arms and links, make sure the threaded ends are plugged. It is

important not to get sand or powder in these areas as it can damage the threads.

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IRS Assembly Steps These steps are written in the order of assembly process. Due to the complexity of this

suspension, it is recommended to take photos before the unit is disassembled.

1. Backing plates/Knuckles/Hubs (Figure 1 & 2)

a. Install the backing plate onto the knuckle, but do not install nuts (PN 73400990).

The backing plates are stamped on the inside face as to which side it should

reside on. The opening of the emergency brake cable pull hook should be facing

away from the toe link boss on the knuckle.

b. Install hubs onto knuckle/backing plate assembly and tighten all three bolts to 96

lb-ft using red Loctite.

c. Tighten backing plate nuts to 25 lb-ft.

d. Thread the toe link stud into the knuckle with red Loctite and torque to 60 lb-ft.

2. Differential (Figure 3 & 4)

a. Install the front differential double shear bracket onto the cradle with all three

bolts and nuts, but do not tighten. Place cradle upside down and start by putting

the rear bushing (on differential cover) into the cradle bracket. A little grease on

the urethane will help the bushing slide in. Insert the bolt with nut, but do not

tighten. Rotate the differential about the rear mount bolt until the front mount

holes line up with the cradle mounts and insert bolts to hold in place. Next,

install nuts and tighten until snug. Now tighten the three double shear bracket

bolts to 25-lb-ft, then tighten all three differential mount bolts to 50 lb-ft. Tip:

To ease differential removal when the cradle is installed in the vehicle, the front

differential mount bolts may need to be inserted from the front or back side to

prevent the bolt from hitting the floor pan when removing.

3. Axles

a. Place inner CV onto differential stub flange and insert all six bolts, using two

washers on each bolt, and tighten evenly until snug. Blue Loctite is

recommended on inner CV bolts. Next, tighten all six bolts to 57 lb-ft.

b. Rotate pinion and make sure CV bolts are not contacting the inner stub retainer

bolts.

4. Anti-Sway Bar (Figure 5)

a. The anti-sway bar is a two piece design to facilitate installation. First, install the

mounting bushings onto the halves. Install the bar halves into the cradle making

sure the bar is over the cradle’s round tube and under the drive axle. Secure

both halves together with the case nut and tighten to about 35 lb-ft. Place the

mount bushings onto the cradle brackets and tighten the 3/8” bolts to 30 lb-ft.

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Next, center the bar by using any reference point and install clamp collars to the

inside of the mount bushings to prevent any lateral movement.

5. Control Arms

a. Before installing the upper control arm, smear a small amount of grease on the

urethane bushings to help slide the bushings into the cradle bracket. Insert the

control arm into the cradle brackets and install bolts and nuts. Do not tighten

until the end of the install process. (Figure 6)

b. Insert the front lower arm into the cradle bracket. Insert the 5/8” bolt from the

front side and install the nut. Tighten the bolt and nut to 90lb-ft. (Figure 7)

c. Insert the rear lower arm into the cradle bracket. Using the 5/8” eccentric bolt,

insert the bolt from the rear and place the front eccentric washer on the bolt.

Rotate the eccentric assembly such it is mid-way through its adjustment range,

at this point the middle hash mark should be in-line with the small indicator hole

in the chassis bracket. Tighten bolt and nut to 90 lb-ft. (Figure 8)

6. Toe Link (Figure 9)

a. Using the eccentric bolt, install the RH rod end of the toe link with misalignment

bushings into the cradle bracket and place the front eccentric washer on the

bolt. Clock the eccentric at the pre-defined mark to ensure proper toe-steer.

Tighten the eccentric nut to 45 lb-ft.

7. Knuckle Assembly

a. Before installing the knuckle, apply a small amount of grease to the CV outer

splines. Next, install the knuckle with hub on to the CV splines as far as possible

by hand. Install the outer CV nut hand tight.

b. Install the knuckle assembly onto the front lower arm. Insert bolt from the front

side, install the nut and torque to 75lb-ft. Install the knuckle onto the rear lower

arm. Insert the bolt from the rear side, install the nut and torque to 75lb-ft.

Install the upper control arm onto the knuckle assembly. Insert the bolt from the

rear side, install the nut and torque to 75lb-ft.

c. Install the toe link onto the knuckle. Install washer with nut and torque to 20lb-

ft.

8. Final Torque of UCA Bolts and Axle Nut

a. Tighten all four upper control arm 5/8” bolts to 90lb-ft.

b. Tighten both axle nuts (at hub) to 150 lb-ft.

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9. Cradle Bushings

a. Smear a small amount of grease into the bushing cup and the bushing inner

bore, and press in the bushings. Next, press in the bushing sleeve until it is flush

with the bottom of the bushing bracket.

Finalizing the Installation When finishing the installation process, the three main steps are: cradle installation, coilover

installation, and wheel alignment.

1. Cradle Installation

When installing the cradle into the vehicle, it should be done when the cradle is fully

assembled. When installing the chassis in a GT Sport chassis (with cradle mount

brackets pre-installed onto the frame), simply position the IRS cradle in the approximate

location and lower the vehicle onto the cradle (or vice-versa if not using a vehicle lift).

Once the IRS cradle bushings have made contact with the frame brackets, it is time to

check for cradle alignment. If the IRS is being installed onto an existing frame that does

not have cradle mount brackets, bolt the frame bracket to the cradle and start the

alignment process. When completed, the frame brackets can be welded to the frame.

Tip: The rear cradle bolts should have the nut at the top side.

Start by aligning the cradle by checking for square. The object is to make sure the cradle

is centered in the vehicle, setting correct longitudinal location (to obtain the correct

wheelbase), and minimizing the thrust angle (the rotation of the cradle in the vehicle’s

frame when looking from the top).

i) Centering: By choosing any reference point on the cradle, measure between these

points to the vehicle’s frame on the left and right sides. Try to equalize the distance

to at least 1/16” or better.

ii) Wheelbase: Determine if the hub is centered in the wheel well opening. While the

actual wheelbase dimension should be close to stock, it is advisable to center the

wheel in the body opening regardless of what the wheelbase dimension is. Slide the

cradle front to back to fine-tune the wheelbase.

iii) Thrust angle: This metric ensures the cradle is rotated correctly in the vehicle’s

frame. By using any reference point on the cradle, measure from these points to

any other critical datum on the vehicle on left and right sides. These dimensions

should be within 1/32” of each other.

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When all three specifications have been adjusted, re-start the alignment process to

make sure some adjustments have not effected previous adjustments. When satisfied

with the alignment, tighten all four cradle bolts to 75 LB-FT.

2) Coilover Installation

The coilovers will attach to the rear lower control arm and up to the vehicle’s frame. Start

by raising the coilover towards the frame mount through the upper control arm. When the

coilover is inserted into the frame brackets, slide the bolt into place. Next, place the

coilover’s lower bearing into the lower control arm and torque until snug. Before tightening

the mounting bolts, check to make sure there is sufficient clearance between the coilover

spring and the upper control arm, as well as the sway bar, throughout the suspension’s

range of travel. This can be done without the spring installed by measuring these areas and

making sure they are greater than the spring’s radius. Manufactures of springs use various

wire diameters, so these dimensions should always be checked. When satisfied, torque the

lower coilover bolt to 60 LB-FT and the upper to 75 LB-FT.

3) Wheel Alignment

The suspensions leaves Art Morrison Enterprises with an alignment that is roughed-in such

the vehicle can be driven to the alignment shop.

Because the multi-link design is becoming more common on modern vehicles, most

alignment shops should not have a problem when aligning this suspension. To get the most

out of the alignment, please follow these tips:

a) Fill the fuel tank ½ to ¾ full

b) Place weights in the driver’s seat to simulate the driver’s weight

c) Scale the vehicle and correct cross weight

d) Set sway bar pre-load to zero (such there is no load on the sway bar at ride height)

e) Have all coilovers set to the proper ride height. To determine the correct ride height,

please review Figure 10. This illustrates the centerline of the coilover mount bolt is 2-½”

lower than the cradle mount bolt centerline.

f) All fluids topped off

Technical Notes

Choosing Spring Rates

Due to the motion ratio of an independent rear suspension, the spring rates are typically

higher than a solid axle suspension, although the actual rate at the wheel is the same or

less. If converting from a solid axle to the Multi-link IRS, divide the old spring rate by 0.6 to

figure the new spring rate. If no previous spring rate is known, use the same rate as the

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front or call Art Morrison Enterprises for assistance. Generally, the springs need to be stiff

enough to prevent bottoming in a hard bump, but soft enough for a comfortable ride

quality. To get the most out of the suspension, try several rates to find one that works best.

Accurately predicting the proper rate is a complex process and is out of the scope of this

manual.

Adjusting Alignment Settings

a) Camber: Before the vehicle is driven, first make rough camber adjustments by adjusting

the rear lower control arm rod end. Shortening the control arm will decrease negative

camber. When camber is close to specification, use the eccentric to make fine

adjustments. Each mark inscribed on the eccentric should be approximately ¼ degree of

camber. Please make sure the camber on both left and right is equal.

b) Caster: The suspension will leave Art Morrison Enterprises with a caster setting that will

work well with lower camber angles. Caster angle is determined by a line drawn in

between the brake caliper bolt centerlines. To measure caster, insert caliper bolts into

the knuckle and place a protractor on the bolts’ shank. This measurement, referenced

from vertical, is the caster angle.

c) Toe: Toe is changed by loosening the rod end jam nuts and twisting the toe link. When

the proper toe is achieved, make sure the jam nuts are tightened securely. Please make

sure the toe on both left and right is equal. Make sure the toe link eccentric is not

adjusted, as this will drastically change the vehicle’s “at-the-limit” behavior! The

eccentric may be confused by some alignment professionals as the toe adjustment,

when it actually controls bumpsteer.

Typical Street Alignment Settings

Camber: 0.75 to 1.25 degrees negative

Caster: 5.8 degrees

Toe: 0.06 to 0.12 degrees total positive (in)

Baseline Race Alignment Settings

Camber: 1 degree less than front camber

i.e. Front camber set at -2.5 degrees, set rear to -1.5 degrees

Caster: 7.2 degrees

Toe: 0 to 0.06 degrees positive (in)

Please note these are baseline settings and will require tuning for proper vehicle behavior.

Toe Link Eccentric Adjustment

As stated in page 3, the toe link eccentric will determine the amount of steering the suspension geometry will act upon the wheel while cornering. Raising the toe link (on

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the cradle) will increase maximum steering angle, and lowering the toe link will decrease the maximum steering angle.

The setting provided by Art Morrison Enterprises offers a conservative level of steering that will noticeably increase turn-in response without adding oversteer. Only experienced suspension tuners and drivers should experiment with this parameter as increasing the steer angle in a careless manner could add an unexpected amount of oversteer. If the vehicle will not see any track use, it is not recommended to adjust the eccentric.

As a general guideline for track use, these situations may benefit from increasing the steering angle:

a. Vehicles with long wheelbases b. Oversized rear tires c. Vehicles with excessive front weight d. Vehicles with excessive understeer e. Vehicles with very low center of gravity

As a general guideline for track use, these situations may benefit from decreasing the steering angle:

a. Vehicles with short wheelbases b. Undersized rear tires c. Vehicles with excessive rear weight d. Vehicles with excessive oversteer e. Vehicles with high center of gravity f. Vehicles with large amounts of power

Bumpstops

Whenever possible, bumpstops should be used to limit bump travel before a control arm (or other component) contacts any part of the cradle or vehicle frame. Bumpstops may be installed on the coilover shaft, or between the vehicle’s frame and upper control arm.

Wheel Sizes

Careful attention needs to be paid to choosing wheel sizes to avoid costly interference

issues. Listed below are specifications to consider:

a. Wheel diameter: The diameter of the wheel needs to be able to clear the brake

caliper. Please note that some 18” wheels may fit, however brake clearance

diagrams provided by the brake manufacturer must be carefully studied to

ensure there is proper clearance between the caliper and wheel hoop. If using

the AME floating caliper brake kit, notice the caliper placement will allow for a

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17” wheel but backspace availability will be severely limited due to lower rear

control arm clearance.

b. Hub to spoke clearance: The lateral distance between the inside spoke face and

the wheel mount surface is critical to ensure the brake caliper will fit. Unlike

older brake designs, the caliper face overhangs the wheel mount surface. Follow

the brake manufacturer’s diagrams to avoid problems.

c. Backspacing: When using an 18” wheel, the backspace must be limited to 7” to

prevent the lower control arm from contacting the wheel hoop at full bump. To

alleviate this, use 19” or larger wheels.

Parking Brake

Regardless of your choice of brake system, the knuckle will be equipped with standard parking brake components for a 2010-up Chevrolet Camaro. This system is a traditional drum-in-hat parking brake that is simple and very functional.

Before installing the brake caliper, be sure to adjust the star wheel on the parking brake to minimize clearance between the brake shoe and rotor drum. Simply adjust the star wheel until slight drag is felt when rotating the rotor, then back off a couple clicks.

Art Morrison Enterprises offers a simple parking brake adapter, part number 14155823, to connect a Lokar parking brake cable to the knuckle. The adapter simply screws onto the Lokar cable then fits into the parking brake cable boss on the knuckle. Slight modification may be needed on the clevis to fit within the knuckle cavity when connecting to the parking brake lever.

Differential Oil

All IRS suspensions are shipped with the differential filled with oil and are ready for break-in,

although the oil level should be checked before the first test drive. Strange S60 differentials

require 64oz of 85W-140 GL-5 oil combined with at least one bottle of friction modifier if a

clutch–type limited slip is used. GM differentials require 1 quart of 75W-90 GL-5 oil combined

with one bottle of friction modifier.

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Figure 1 - Knuckle Assembly

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Figure 2 - Knuckle Assembly

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Figure 3 - Differential Assembly

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Figure 4 - Differential Assembly

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Figure 5 - Sway Bar Assembly

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Figure 6 - Upper Control Arm Assembly

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Figure 7 - Front Lower Control Arm Assembly

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Figure 8 - Rear Lower Control Arm Assembly

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Figure 9 – Toe Link Assembly

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Figure 10 - Ride Height Specification

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Figure 11 - LH Link Length Worksheet

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Figure 12 - RH Link Length Worksheet

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Fastener Location Size Thread Pitch Grade

Torque (LB-FT) Notes

UCA - Cradle 5/8 X 3.5 NF 8 90

Rear LCA - Cradle 5/8 X 3.25 NF 8 90

Front LCA - Cradle 5/8 X 3 NF 8 90

Toe Link - Cradle 1/2 X 2 NF 5 45

UCA - Knuckle M12 X 80 1.75 10.9 75

Rear LCA - Knuckle M12 X 80 1.75 10.9 75

Front LCA - Knuckle M12 X 80 1.75 10.9 75

Toe Link Nut - Knuckle 3/8 NF 5 20

Rear Diff M12 x 90 1.75 10.9 50

Front Diff M12 x 90 1.75 10.9 50

Diff Cover (GM Diff) M10 x 35 1.5 8.8 30

Diff Cover (Strange Diff) 3/8 X 1 NC 5 25

Diff Support Bracket 3/8 X 1 NC 8 25

Axle to Inner CV (Strange Only) M10 x 60 1.5 12.9 57 Blue Loctite

CV Axle to Hub

150 34MM Hex

Lower Coilover 1/2 X 4.5 NC 8 60 Anti-seize

ARB Bracket 3/8 X 1 NC 8 30

Hub to Knuckle M12 x 60 1.75 12.9 96 Red Loctite

Parking Brake Plate to Knuckle M10 1.5 25

Caliper to Knuckle M12 X 51 1.75 12.9 65 Red Loctite

Cradle to Frame Bracket 1/2 X 3.25 NF 8 75 Figure 13 - Fasteners & Torque Specifications